One major concern for operators of large-scale generators (e.g. a steam turbine generator, a gas turbine generator, or a hydroelectric generator) is the potential hazard of an arc flash event at the generator excitation system. For example, the arc flash event can cause damage to generator system components, undesirably impact the power output by the generator, and, perhaps most importantly, cause injury or death to personnel located proximate to the event.
For certain generators, a switchgear can be placed between the power potential transformer and the generator excitation system to provide protection against an arc flash event inside the exciter. However, there is a lack of switchgears with a sufficient rating to capably handle the increased energy levels associated with certain large-scale generators.
Furthermore, typical switchgear opening times range from about 5 to 6 cycles. A longer total clearing time by the protection device generally results in larger incident energies and, thus, a greater hazard resulting from an arc flash event. Therefore, in certain circumstances, switchgears can operate too slowly to sufficiently mitigate the arc flash hazard.
Therefore, arc flash mitigation systems that provide a smaller total clearing time and that can properly operate at the energy levels used by generator excitation systems of large-scale generators are desirable.